Monitoring the Development of Cotton (Gossypium barbadense L.) using Emission Spectra of Chlorophyll Fluorescence

This work was proposed to monitor the growth and development of cotton (Gossypium barbadense L.) under different environmental conditions using emission spectra of chlorophyll a fluorescence from the intact leaves. The emitted fluorescence signal by cotton plants was measured using spectrometer/graphic and data analysis software. Cotton was grown in the summer season under sunlight exposure i.e. summer conditions, whereas in winter conditions the plants were grown in a shaded area. Both groups of plants were irrigated by tap water. Winter conditions exhibit environmental stress of temperature and light intensity. Monochromatic blue light of 450 nm was used as an excitation source to induce the chlorophyll fluorescence emission at 685 nm and 733 nm. The peak intensity ratio (P.I.R.), which is the ratio between maximum emitted light intensities at 685 nm and 733 nm respectively (IF685/IF733), and the area ratio (A.R.) which is the ratio between the areas under the curves of the two emission lines were used for monitoring the development of cotton, from the germination until the flowering. The results revealed that the summer conditions gave a faster seed germination rate and the best growth and development of cotton, while the stressing winter conditions expressed in delayed seed germination, poor growth that led to failure of flowering and immaturity. The peak intensity ratio and area ratio for the summer and winter conditions were found to follow linear relationships. The line slopes of the peak intensity ratio and area ratios were 1.36 and 0.46 and the intercepts were 0.04 and 0.04 respectively.